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Piro F, Masci S, Kannan G, Focaia R, Schultz TL, Thaprawat P, Carruthers VB, Di Cristina M. A Toxoplasma gondii putative amino acid transporter localizes to the plant-like vacuolar compartment and controls parasite extracellular survival and stage differentiation. mSphere 2024; 9:e0059723. [PMID: 38051073 PMCID: PMC10871165 DOI: 10.1128/msphere.00597-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 10/26/2023] [Indexed: 12/07/2023] Open
Abstract
Toxoplasma gondii is a protozoan parasite that infects a broad spectrum of hosts and can colonize many organs and cell types. The ability to reside within a wide range of different niches requires substantial adaptability to diverse microenvironments. Very little is known about how this parasite senses various milieus and adapts its metabolism to survive, replicate during the acute stage, and then differentiate to the chronic stage. T. gondii possesses a lysosome-like organelle known as the plant-like vacuolar compartment (PLVAC), which serves various functions, including digestion, ion storage and homeostasis, endocytosis, and autophagy. Lysosomes are critical for maintaining cellular health and function by degrading waste materials and recycling components. To supply the cell with the essential building blocks and energy sources required for the maintenance of its functions and structures, the digested solutes generated within the lysosome are transported into the cytosol by proteins embedded in the lysosomal membrane. Currently, a limited number of PLVAC transporters have been characterized, with TgCRT being the sole potential transporter of amino acids and small peptides identified thus far. To bridge this knowledge gap, we used lysosomal amino acid transporters from other organisms as queries to search the T. gondii proteome. This led to the identification of four potential amino acid transporters, which we have designated as TgAAT1-4. Assessing their expression and sub-cellular localization, we found that one of them, TgAAT1, localized to the PLVAC and is necessary for normal parasite extracellular survival and bradyzoite differentiation. Moreover, we present preliminary data showing the possible involvement of TgAAT1 in the PLVAC transport of arginine.IMPORTANCEToxoplasma gondii is a highly successful parasite infecting a broad range of warm-blooded organisms, including about one-third of all humans. Although Toxoplasma infections rarely result in symptomatic disease in individuals with a healthy immune system, the incredibly high number of persons infected, along with the risk of severe infection in immunocompromised patients and the potential link of chronic infection to mental disorders, makes this infection a significant public health concern. As a result, there is a pressing need for new treatment approaches that are both effective and well tolerated. The limitations in understanding how Toxoplasma gondii manages its metabolism to adapt to changing environments and triggers its transformation into bradyzoites have hindered the discovery of vulnerabilities in its metabolic pathways or nutrient acquisition mechanisms to identify new therapeutic targets. In this work, we have shown that the lysosome-like organelle plant-like vacuolar compartment (PLVAC), acting through the putative arginine transporter TgAAT1, plays a pivotal role in regulating the parasite's extracellular survival and differentiation into bradyzoites.
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Affiliation(s)
- Federica Piro
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Silvia Masci
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Geetha Kannan
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Riccardo Focaia
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Tracey L. Schultz
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Pariyamon Thaprawat
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Vern B. Carruthers
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Manlio Di Cristina
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
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Thornton LB, Key M, Micchelli C, Stasic AJ, Kwain S, Floyd K, Moreno SN, Dominy BN, Whitehead DC, Dou Z. A cathepsin C-like protease mediates the post-translation modification of Toxoplasma gondii secretory proteins for optimal invasion and egress. mBio 2023; 14:e0017423. [PMID: 37326431 PMCID: PMC10470614 DOI: 10.1128/mbio.00174-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 05/01/2023] [Indexed: 06/17/2023] Open
Abstract
Microbial pathogens use proteases for their infections, such as digestion of proteins for nutrients and activation of their virulence factors. As an obligate intracellular parasite, Toxoplasma gondii must invade host cells to establish its intracellular propagation. To facilitate invasion, the parasites secrete invasion effectors from microneme and rhoptry, two unique organelles in apicomplexans. Previous work has shown that some micronemal invasion effectors experience a series of proteolytic cleavages within the parasite's secretion pathway for maturation, such as the aspartyl protease (TgASP3) and the cathepsin L-like protease (TgCPL), localized within the post-Golgi compartment and the endolysosomal system, respectively. Furthermore, it has been shown that the precise maturation of micronemal effectors is critical for Toxoplasma invasion and egress. Here, we show that an endosome-like compartment (ELC)-residing cathepsin C-like protease (TgCPC1) mediates the final trimming of some micronemal effectors, and its loss further results in defects in the steps of invasion, egress, and migration throughout the parasite's lytic cycle. Notably, the deletion of TgCPC1 completely blocks the activation of subtilisin-like protease 1 (TgSUB1) in the parasites, which globally impairs the surface-trimming of many key micronemal invasion and egress effectors. Additionally, we found that Toxoplasma is not efficiently inhibited by the chemical inhibitor targeting the malarial CPC ortholog, suggesting that these cathepsin C-like orthologs are structurally different within the apicomplexan phylum. Collectively, our findings identify a novel function of TgCPC1 in processing micronemal proteins within the Toxoplasma parasite's secretory pathway and expand the understanding of the roles of cathepsin C protease. IMPORTANCE Toxoplasma gondii is a microbial pathogen that is well adapted for disseminating infections. It can infect virtually all warm-blooded animals. Approximately one-third of the human population carries toxoplasmosis. During infection, the parasites sequentially secrete protein effectors from the microneme, rhoptry, and dense granule, three organelles exclusively found in apicomplexan parasites, to help establish their lytic cycle. Proteolytic cleavage of these secretory proteins is required for the parasite's optimal function. Previous work has revealed that two proteases residing within the parasite's secretory pathway cleave micronemal and rhoptry proteins, which mediate parasite invasion and egress. Here, we demonstrate that a cathepsin C-like protease (TgCPC1) is involved in processing several invasion and egress effectors. The genetic deletion of TgCPC1 prevented the complete maturation of some effectors in the parasites. Strikingly, the deletion led to a full inactivation of one surface-anchored protease, which globally impaired the trimming of some key micronemal proteins before secretion. Therefore, this finding represents a novel post-translational mechanism for the processing of virulence factors within microbial pathogens.
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Affiliation(s)
- L. Brock Thornton
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, USA
| | - Melanie Key
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, USA
| | - Chiara Micchelli
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, USA
| | - Andrew J. Stasic
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Samuel Kwain
- Department of Chemistry, Clemson University, Clemson, South Carolina, USA
| | - Katherine Floyd
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, USA
| | - Silvia N.J. Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Brian N. Dominy
- Department of Chemistry, Clemson University, Clemson, South Carolina, USA
| | - Daniel C. Whitehead
- Department of Chemistry, Clemson University, Clemson, South Carolina, USA
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, South Carolina, USA
| | - Zhicheng Dou
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, USA
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, South Carolina, USA
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3
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Thornton LB, Key M, Micchelli C, Stasic AJ, Kwain S, Floyd K, Moreno SNJ, Dominy BN, Whitehead DC, Dou Z. A cathepsin C-like protease post-translationally modifies Toxoplasma gondii secretory proteins for optimal invasion and egress. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.21.525043. [PMID: 36712013 PMCID: PMC9882377 DOI: 10.1101/2023.01.21.525043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Microbial pathogens use proteases for their infections, such as digestion of proteins for nutrients and activation of their virulence factors. As an obligate intracellular parasite, Toxoplasma gondii must invade host cells to establish its intracellular propagation. To facilitate invasion, the parasites secrete invasion effectors from microneme and rhoptry, two unique organelles in apicomplexans. Previous work has shown that some micronemal invasion effectors experience a series of proteolytic cleavages within the parasite's secretion pathway for maturation, such as the aspartyl protease (TgASP3) and the cathepsin L-like protease (TgCPL), localized within the post-Golgi compartment (1) and the endolysosomal system (2), respectively. Furthermore, it has been shown that the precise maturation of micronemal effectors is critical for Toxoplasma invasion and egress (1). Here, we show that an endosome-like compartment (ELC)-residing cathepsin C-like protease (TgCPC1) mediates the final trimming of some micronemal effectors, and its loss further results in defects in the steps of invasion, egress, and migration throughout the parasite's lytic cycle. Notably, the deletion of TgCPC1 completely blocks the activation of subtilisin-like protease 1 (TgSUB1) in the parasites, which globally impairs the surface-trimming of many key micronemal invasion and egress effectors. Additionally, we found that TgCPC1 was not efficiently inhibited by the chemical inhibitor targeting its malarial ortholog, suggesting that these cathepsin C-like orthologs are structurally different within the apicomplexan phylum. Taken together, our findings identify a novel function of TgCPC1 in the processing of micronemal proteins within the secretory pathway of Toxoplasma parasites and expand the understanding of the roles of cathepsin C protease. IMPORTANCE Toxoplasma gondii is a microbial pathogen that is well adapted for disseminating infections. It can infect virtually all warm-blooded animals. Approximately one-third of the human population carries toxoplasmosis. During infection, the parasites sequentially secrete protein effectors from the microneme, rhoptry, and dense granule, three organelles exclusively found in apicomplexan parasites, to help establish their lytic cycle. Proteolytic cleavage of these secretory proteins is required for the parasite's optimal function. Previous work has revealed that two proteases residing within the parasite's secretory pathway cleave micronemal and rhoptry proteins, which mediate parasite invasion and egress. Here, we demonstrate that a cathepsin C-like protease (TgCPC1) is involved in processing several invasion and egress effectors. The genetic deletion of TgCPC1 prevented the complete maturation of some effectors in the parasites. Strikingly, the deletion led to a full inactivation of one surface-anchored protease, which globally impaired the trimming of some key micronemal proteins before secretion. Therefore, this finding represents a novel post-translational mechanism for the processing of virulence factors within microbial pathogens.
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Affiliation(s)
- L. Brock Thornton
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Melanie Key
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Chiara Micchelli
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Andrew J. Stasic
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
- Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Samuel Kwain
- Department of Chemistry, Clemson University, Clemson, South Carolina, United States of America
| | - Katherine Floyd
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Silvia N. J. Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
- Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Brian N. Dominy
- Department of Chemistry, Clemson University, Clemson, South Carolina, United States of America
| | - Daniel C. Whitehead
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, South Carolina, United States of America
- Department of Chemistry, Clemson University, Clemson, South Carolina, United States of America
| | - Zhicheng Dou
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
- Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, South Carolina, United States of America
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4
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Stasic AJ, Moreno SNJ, Carruthers VB, Dou Z. The Toxoplasma plant-like vacuolar compartment (PLVAC). J Eukaryot Microbiol 2022; 69:e12951. [PMID: 36218001 PMCID: PMC10576567 DOI: 10.1111/jeu.12951] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 10/06/2022] [Accepted: 10/07/2022] [Indexed: 11/28/2022]
Abstract
Toxoplasma gondii belongs to the phylum Apicomplexa and is an important cause of congenital disease and infection in immunocompromised patients. T. gondii shares several characteristics with plants including a nonphotosynthetic plastid termed apicoplast and a multivesicular organelle that was named the plant-like vacuole (PLV) or vacuolar compartment (VAC). The name plant-like vacuole was selected based on its resemblance in composition and function to plant vacuoles. The name VAC represents its general vacuolar characteristics. We will refer to the organelle as PLVAC in this review. New findings in recent years have revealed that the PLVAC represents the lysosomal compartment of T. gondii which has adapted peculiarities to fulfill specific Toxoplasma needs. In this review, we discuss the composition and functions of the PLVAC highlighting its roles in ion storage and homeostasis, endocytosis, exocytosis, and autophagy.
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Affiliation(s)
- Andrew J Stasic
- Department of Microbiology, Heartland FPG, Carmel, Indiana, USA
| | - Silvia N J Moreno
- Department of Cellular Biology, University of Georgia, Georgia, Athens, USA
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Georgia, Athens, USA
| | - Vern B Carruthers
- Department of Microbiology & Immunology, University of Michigan Medical School, Michigan, Ann Arbor, USA
| | - Zhicheng Dou
- Department of Biological Sciences, Clemson University, South Carolina, Clemson, USA
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5
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The Autophagy Machinery in Human-Parasitic Protists; Diverse Functions for Universally Conserved Proteins. Cells 2021; 10:cells10051258. [PMID: 34069694 PMCID: PMC8161075 DOI: 10.3390/cells10051258] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/17/2021] [Accepted: 05/18/2021] [Indexed: 12/31/2022] Open
Abstract
Autophagy is a eukaryotic cellular machinery that is able to degrade large intracellular components, including organelles, and plays a pivotal role in cellular homeostasis. Target materials are enclosed by a double membrane vesicle called autophagosome, whose formation is coordinated by autophagy-related proteins (ATGs). Studies of yeast and Metazoa have identified approximately 40 ATGs. Genome projects for unicellular eukaryotes revealed that some ATGs are conserved in all eukaryotic supergroups but others have arisen or were lost during evolution in some specific lineages. In spite of an apparent reduction in the ATG molecular machinery found in parasitic protists, it has become clear that ATGs play an important role in stage differentiation or organelle maintenance, sometimes with an original function that is unrelated to canonical degradative autophagy. In this review, we aim to briefly summarize the current state of knowledge in parasitic protists, in the light of the latest important findings from more canonical model organisms. Determining the roles of ATGs and the diversity of their functions in various lineages is an important challenge for understanding the evolutionary background of autophagy.
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6
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Zwicker JD, Smith D, Guerra AJ, Hitchens JR, Haug N, Vander Roest S, Lee P, Wen B, Sun D, Wang L, Keep RF, Xiang J, Carruthers VB, Larsen SD. Discovery and Optimization of Triazine Nitrile Inhibitors of Toxoplasma gondii Cathepsin L for the Potential Treatment of Chronic Toxoplasmosis in the CNS. ACS Chem Neurosci 2020; 11:2450-2463. [PMID: 32027110 DOI: 10.1021/acschemneuro.9b00674] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
With roughly 2 billion people infected, the neurotropic protozoan Toxoplasma gondii remains one of the most pervasive and infectious parasites. Toxoplasma infection is the second leading cause of death due to foodborne illness in the United States, causes severe disease in immunocompromised patients, and is correlated with several cognitive and neurological disorders. Currently, no therapies exist that are capable of eliminating the persistent infection in the central nervous system (CNS). In this study we report the identification of triazine nitrile inhibitors of Toxoplasma cathepsin L (TgCPL) from a high throughput screen and their subsequent optimization. Through rational design, we improved inhibitor potency to as low as 5 nM, identified pharmacophore features that can be exploited for isoform selectivity (up to 7-fold for TgCPL versus human isoform), and improved metabolic stability (t1/2 > 60 min in mouse liver microsomes) guided by a metabolite ID study. We demonstrated that this class of compounds is capable of crossing the blood-brain barrier in mice (1:1 brain/plasma at 2 h). Importantly, we also show for the first time that treatment of T. gondii bradyzoite cysts in vitro with triazine nitrile inhibitors reduces parasite viability with efficacy equivalent to a TgCPL genetic knockout.
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Affiliation(s)
- Jeffery D. Zwicker
- Vahlteich Medicinal Chemistry Core, College of Pharmacy, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - David Smith
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Alfredo J. Guerra
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Jacob R. Hitchens
- Vahlteich Medicinal Chemistry Core, College of Pharmacy, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nicole Haug
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Steve Vander Roest
- Center for Chemical Genomics, Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Pil Lee
- Vahlteich Medicinal Chemistry Core, College of Pharmacy, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Bo Wen
- Pharmacokinetics Core, Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Duxin Sun
- Pharmacokinetics Core, Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Lu Wang
- Pharmacokinetics Core, Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Richard F. Keep
- Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Jianming Xiang
- Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Vern B. Carruthers
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Scott D. Larsen
- Vahlteich Medicinal Chemistry Core, College of Pharmacy, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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Stasic AJ, Chasen NM, Dykes EJ, Vella SA, Asady B, Starai VJ, Moreno SNJ. The Toxoplasma Vacuolar H +-ATPase Regulates Intracellular pH and Impacts the Maturation of Essential Secretory Proteins. Cell Rep 2020; 27:2132-2146.e7. [PMID: 31091451 PMCID: PMC6760873 DOI: 10.1016/j.celrep.2019.04.038] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 10/31/2018] [Accepted: 04/05/2019] [Indexed: 12/20/2022] Open
Abstract
Vacuolar-proton ATPases (V-ATPases) are conserved complexes that couple the hydrolysis of ATP to the pumping of protons across membranes. V-ATPases are known to play diverse roles in cellular physiology. We studied the Toxoplasma gondii V-ATPase complex and discovered a dual role of the pump in protecting parasites against ionic stress and in the maturation of secretory proteins in endosomal-like compartments. Toxoplasma V-ATPase subunits localize to the plasma membrane and to acidic vesicles, and characterization of conditional mutants of the a1 subunit highlighted the functionality of the complex at both locations. Microneme and rhoptry proteins are required for invasion and modulation of host cells, and they traffic via endosome-like compartments in which proteolytic maturation occurs. We show that the V-ATPase supports the maturation of rhoptry and microneme proteins, and their maturases, during their traffic to their corresponding organelles. This work underscores a role for V-ATPases in regulating virulence pathways. Stasic et al. characterize the function of the vacuolar proton ATPase in the life cycle of Toxoplasma gondii, a widespread parasite that infects almost one-third of the world’s population. The work presents molecular evidence of the pump’s role in the synthesis of virulence factors of a highly successful pathogen.
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Affiliation(s)
- Andrew J Stasic
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA; Department of Microbiology, University of Georgia, Athens, GA 30602-7400, USA
| | - Nathan M Chasen
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA; Department of Infectious Diseases, University of Georgia, Athens, GA 30602-7400, USA
| | - Eric J Dykes
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA
| | - Stephen A Vella
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA; Department of Microbiology, University of Georgia, Athens, GA 30602-7400, USA
| | - Beejan Asady
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA
| | - Vincent J Starai
- Department of Microbiology, University of Georgia, Athens, GA 30602-7400, USA; Department of Infectious Diseases, University of Georgia, Athens, GA 30602-7400, USA
| | - Silvia N J Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602-7400, USA; Department of Cellular Biology, University of Georgia, Athens, GA 30602-7400, USA.
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Toxoplasma Cathepsin Protease B and Aspartyl Protease 1 Are Dispensable for Endolysosomal Protein Digestion. mSphere 2020; 5:5/1/e00869-19. [PMID: 32051238 PMCID: PMC7021471 DOI: 10.1128/msphere.00869-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Roughly one-third of the human population is chronically infected with the intracellular single-celled parasite Toxoplasma gondii, but little is known about how this organism persists inside people. Previous research suggested that a parasite proteolytic enzyme, termed cathepsin protease L, is important for Toxoplasma persistence; however, it remained possible that other associated proteolytic enzymes could also be involved in the long-term survival of the parasite during infection. Here, we show that two proteolytic enzymes associated with cathepsin protease L play dispensable roles and are dependent on cathepsin L to reach maturity, which differs from the corresponding enzymes in humans. These findings establish a divergent hierarchy of proteases and help focus attention principally on cathepsin protease L as a potential target for interrupting Toxoplasma chronic infection. The lysosome-like vacuolar compartment (VAC) is a major site of proteolysis in the intracellular parasite Toxoplasma gondii. Previous studies have shown that genetic ablation of a VAC-residing cysteine protease, cathepsin protease L (CPL), resulted in the accumulation of undigested protein in the VAC and loss of parasite viability during the chronic stage of infection. However, since the maturation of another VAC localizing protease, cathepsin protease B (CPB), is dependent on CPL, it remained unknown whether these defects result directly from ablation of CPL or indirectly from a lack of CPB maturation. Likewise, although a previously described cathepsin D-like aspartyl protease 1 (ASP1) could also play a role in proteolysis, its definitive residence and function in the Toxoplasma endolysosomal system were not well defined. Here, we demonstrate that CPB is not necessary for protein turnover in the VAC and that CPB-deficient parasites have normal growth and viability in both the acute and chronic stages of infection. We also show that ASP1 depends on CPL for correct maturation, and it resides in the T. gondii VAC, where, similar to CPB, it plays a dispensable role in protein digestion. Taken together with previous work, our findings suggest that CPL is the dominant protease in a hierarchy of proteolytic enzymes within the VAC. This unusual lack of redundancy for CPL in T. gondii makes it a single exploitable target for disrupting chronic toxoplasmosis. IMPORTANCE Roughly one-third of the human population is chronically infected with the intracellular single-celled parasite Toxoplasma gondii, but little is known about how this organism persists inside people. Previous research suggested that a parasite proteolytic enzyme, termed cathepsin protease L, is important for Toxoplasma persistence; however, it remained possible that other associated proteolytic enzymes could also be involved in the long-term survival of the parasite during infection. Here, we show that two proteolytic enzymes associated with cathepsin protease L play dispensable roles and are dependent on cathepsin L to reach maturity, which differs from the corresponding enzymes in humans. These findings establish a divergent hierarchy of proteases and help focus attention principally on cathepsin protease L as a potential target for interrupting Toxoplasma chronic infection.
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Thornton LB, Teehan P, Floyd K, Cochrane C, Bergmann A, Riegel B, Stasic AJ, Di Cristina M, Moreno SNJ, Roepe PD, Dou Z. An ortholog of Plasmodium falciparum chloroquine resistance transporter (PfCRT) plays a key role in maintaining the integrity of the endolysosomal system in Toxoplasma gondii to facilitate host invasion. PLoS Pathog 2019; 15:e1007775. [PMID: 31170269 PMCID: PMC6553793 DOI: 10.1371/journal.ppat.1007775] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 04/22/2019] [Indexed: 12/13/2022] Open
Abstract
Toxoplasma gondii is an apicomplexan parasite with the ability to use foodborne, zoonotic, and congenital routes of transmission that causes severe disease in immunocompromised patients. The parasites harbor a lysosome-like organelle, termed the "Vacuolar Compartment/Plant-Like Vacuole" (VAC/PLV), which plays an important role in maintaining the lytic cycle and virulence of T. gondii. The VAC supplies proteolytic enzymes that contribute to the maturation of invasion effectors and that digest autophagosomes and endocytosed host proteins. Previous work identified a T. gondii ortholog of the Plasmodium falciparum chloroquine resistance transporter (PfCRT) that localized to the VAC. Here, we show that TgCRT is a membrane transporter that is functionally similar to PfCRT. We also genetically ablate TgCRT and reveal that the TgCRT protein plays a key role in maintaining the integrity of the parasite’s endolysosomal system by controlling morphology of the VAC. When TgCRT is absent, the VAC dramatically increases in volume by ~15-fold and overlaps with adjacent endosome-like compartments. Presumably to reduce aberrant swelling, transcription and translation of endolysosomal proteases are decreased in ΔTgCRT parasites. Expression of subtilisin protease 1 is significantly reduced, which impedes trimming of microneme proteins, and significantly decreases parasite invasion. Chemical or genetic inhibition of proteolysis within the VAC reverses these effects, reducing VAC size and partially restoring integrity of the endolysosomal system, microneme protein trimming, and invasion. Taken together, these findings reveal for the first time a physiological role of TgCRT in substrate transport that impacts VAC volume and the integrity of the endolysosomal system in T. gondii. Toxoplasma gondii is an obligate intracellular protozoan parasite that belongs to the phylum Apicomplexa and that infects virtually all warm-blooded organisms. Approximately one-third of the human population is infected with Toxoplasma. Toxoplasma invades host cells using processed invasion effectors. A lysosome-like organelle (VAC) is involved in refining these invasion effectors to reach their final forms. A T. gondii ortholog of the malarial chloroquine resistance transporter protein (TgCRT) was found to be localized to the VAC membrane. Although the mutated version of the malarial chloroquine resistance transporter (PfCRT) has been shown to confer resistance to chloroquine treatment, its physiologic function remains poorly understood. Comparison between the related PfCRT and TgCRT facilitates definition of the physiologic role of CRT proteins. Here, we report that TgCRT plays a key role in affecting the integrity and proteolytic activity of the VAC and adjacent organelles, the secretion of invasion effectors, and parasite invasion and virulence. To relieve osmotic stress caused by VAC swelling when TgCRT is deleted, parasites repress proteolysis within this organelle to decrease solute accumulation, which then has secondary effects on parasite invasion. Our findings highlight a common function for PfCRT and TgCRT in mediating small solute transport to affect apicomplexan parasite vacuolar size and function.
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Affiliation(s)
- L. Brock Thornton
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Paige Teehan
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Katherine Floyd
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Christian Cochrane
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Amy Bergmann
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Bryce Riegel
- Department of Chemistry, Georgetown University, NW, Washington DC, United States of America
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University, NW, Washington DC, United States of America
| | - Andrew J. Stasic
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
- Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Manlio Di Cristina
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Silvia N. J. Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
- Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Paul D. Roepe
- Department of Chemistry, Georgetown University, NW, Washington DC, United States of America
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University, NW, Washington DC, United States of America
| | - Zhicheng Dou
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
- * E-mail:
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10
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Koeller CM, Bangs JD. Processing and targeting of cathepsin L (TbCatL) to the lysosome in
Trypanosoma brucei. Cell Microbiol 2019; 21:e12980. [DOI: 10.1111/cmi.12980] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 10/29/2018] [Accepted: 11/07/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Carolina M. Koeller
- Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences University at Buffalo (SUNY) Buffalo New York USA
| | - James D. Bangs
- Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences University at Buffalo (SUNY) Buffalo New York USA
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11
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Ramírez-Flores CJ, Cruz-Mirón R, Arroyo R, Mondragón-Castelán ME, Nopal-Guerrero T, González-Pozos S, Ríos-Castro E, Mondragón-Flores R. Characterization of metalloproteases and serine proteases of Toxoplasma gondii tachyzoites and their effect on epithelial cells. Parasitol Res 2018; 118:289-306. [DOI: 10.1007/s00436-018-6163-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 11/22/2018] [Indexed: 02/07/2023]
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12
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Siqueira-Neto JL, Debnath A, McCall LI, Bernatchez JA, Ndao M, Reed SL, Rosenthal PJ. Cysteine proteases in protozoan parasites. PLoS Negl Trop Dis 2018; 12:e0006512. [PMID: 30138453 PMCID: PMC6107107 DOI: 10.1371/journal.pntd.0006512] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Cysteine proteases (CPs) play key roles in the pathogenesis of protozoan parasites, including cell/tissue penetration, hydrolysis of host or parasite proteins, autophagy, and evasion or modulation of the host immune response, making them attractive chemotherapeutic and vaccine targets. This review highlights current knowledge on clan CA cysteine proteases, the best-characterized group of cysteine proteases, from 7 protozoan organisms causing human diseases with significant impact: Entamoeba histolytica, Leishmania species (sp.), Trypanosoma brucei, T. cruzi, Cryptosporidium sp., Plasmodium sp., and Toxoplasma gondii. Clan CA proteases from three organisms (T. brucei, T. cruzi, and Plasmodium sp.) are well characterized as druggable targets based on in vitro and in vivo models. A number of candidate inhibitors are under development. CPs from these organisms and from other protozoan parasites should be further characterized to improve our understanding of their biological functions and identify novel targets for chemotherapy.
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Affiliation(s)
- Jair L. Siqueira-Neto
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
| | - Anjan Debnath
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Laura-Isobel McCall
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Jean A. Bernatchez
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Momar Ndao
- National Reference Centre for Parasitology, The Research Institute of the McGill University Health Center, Montreal, Canada
- Program in Infectious Diseases and Immunity in Global Health, The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Sharon L. Reed
- Departments of Pathology and Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | - Philip J. Rosenthal
- Department of Medicine, University of California, San Francisco, San Francisco, California, United States of America
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13
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Benns HJ, Tate EW, Child MA. Activity-Based Protein Profiling for the Study of Parasite Biology. Curr Top Microbiol Immunol 2018; 420:155-174. [PMID: 30105424 DOI: 10.1007/82_2018_123] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Parasites exist within most ecological niches, often transitioning through biologically and chemically complex host environments over the course of their parasitic life cycles. While the development of technologies for genetic engineering has revolutionised the field of functional genomics, parasites have historically been less amenable to such modification. In light of this, parasitologists have often been at the forefront of adopting new small-molecule technologies, repurposing drugs into biological tools and probes. Over the last decade, activity-based protein profiling (ABPP) has evolved into a powerful and versatile chemical proteomic platform for characterising the function of enzymes. Central to ABPP is the use of activity-based probes (ABPs), which covalently modify the active sites of enzyme classes ranging from serine hydrolases to glycosidases. The application of ABPP to cellular systems has contributed vastly to our knowledge on the fundamental biology of a diverse range of organisms and has facilitated the identification of potential drug targets in many pathogens. In this chapter, we provide a comprehensive review on the different forms of ABPP that have been successfully applied to parasite systems, and highlight key biological insights that have been enabled through their application.
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Affiliation(s)
- Henry J Benns
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Edward W Tate
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Matthew A Child
- Life Sciences, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ, UK.
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14
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Morlon-Guyot J, El Hajj H, Martin K, Fois A, Carrillo A, Berry L, Burchmore R, Meissner M, Lebrun M, Daher W. A proteomic analysis unravels novel CORVET and HOPS proteins involved in Toxoplasma gondii
secretory organelles biogenesis. Cell Microbiol 2018; 20:e12870. [DOI: 10.1111/cmi.12870] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 05/23/2018] [Accepted: 06/05/2018] [Indexed: 01/10/2023]
Affiliation(s)
- Juliette Morlon-Guyot
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Hiba El Hajj
- Departments of Internal Medicine and Experimental Pathology, Immunology and Microbiology; American University of Beirut; Beirut Lebanon
| | - Kevin Martin
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Adrien Fois
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Amandine Carrillo
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Laurence Berry
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | | | - Markus Meissner
- Wellcome Centre for Molecular Parasitology; University of Glasgow; Glasgow UK
- Department of Veterinary Sciences, Experimental Parasitology; Ludwig-Maximilians-Universität München; Munich Germany
| | - Maryse Lebrun
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
| | - Wassim Daher
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, INSERM; Université de Montpellier; Montpellier France
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15
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McGovern OL, Rivera-Cuevas Y, Kannan G, Narwold AJ, Carruthers VB. Intersection of endocytic and exocytic systems in Toxoplasma gondii. Traffic 2018; 19:336-353. [PMID: 29437275 DOI: 10.1111/tra.12556] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 02/09/2018] [Accepted: 02/10/2018] [Indexed: 12/12/2022]
Abstract
Host cytosolic proteins are endocytosed by Toxoplasma gondii and degraded in its lysosome-like compartment, the vacuolar compartment (VAC), but the dynamics and route of endocytic trafficking remain undefined. Conserved endocytic components and plant-like features suggest T. gondii endocytic trafficking involves transit through early and late endosome-like compartments (ELCs) and potentially the trans-Golgi network (TGN) as in plants. However, exocytic trafficking to regulated secretory organelles, micronemes and rhoptries, also proceeds through ELCs and requires classical endocytic components, including a dynamin-related protein, DrpB. Here, we show that host cytosolic proteins are endocytosed within 7 minutes post-invasion, trafficked through ELCs en route to the VAC, and degraded within 30 minutes. We could not definitively interpret if ingested protein is trafficked through the TGN. We also found that parasites ingest material from the host cytosol throughout the parasite cell cycle. Ingested host proteins colocalize with immature microneme proteins, proM2AP and proMIC5, in transit to the micronemes, but not with the immature rhoptry protein proRON4, indicating that endocytic trafficking of ingested protein intersects with exocytic trafficking of microneme proteins. Finally, we show that conditional expression of a DrpB dominant negative mutant increases T. gondii ingestion of host-derived proteins, suggesting that DrpB is not required for parasite endocytosis.
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Affiliation(s)
- Olivia L McGovern
- Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - Yolanda Rivera-Cuevas
- Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - Geetha Kannan
- Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - Andrew J Narwold
- Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - Vern B Carruthers
- Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, Michigan
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16
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Chaparro JD, Cheng T, Tran UP, Andrade RM, Brenner SBT, Hwang G, Cohn S, Hirata K, McKerrow JH, Reed SL. Two key cathepsins, TgCPB and TgCPL, are targeted by the vinyl sulfone inhibitor K11777 in in vitro and in vivo models of toxoplasmosis. PLoS One 2018; 13:e0193982. [PMID: 29565998 PMCID: PMC5863946 DOI: 10.1371/journal.pone.0193982] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 02/19/2018] [Indexed: 01/03/2023] Open
Abstract
Although toxoplasmosis is one of the most common parasitic infections worldwide, therapeutic options remain limited. Cathepsins, proteases that play key roles in the pathogenesis of toxoplasmosis and many other protozoan infections, are important potential therapeutic targets. Because both TgCPB and TgCPL play a role in T. gondii invasion, we evaluated the efficacy of the potent, irreversible vinyl sulfone inhibitor, K11777 (N-methyl-piperazine-Phe-homoPhe-vinylsulfone-phenyl). The inhibitor’s toxicity and pharmacokinetic profile have been well-studied because of its in vitro and in vivo activity against a number of parasites. We found that it inhibited both TgCPB (EC50 = 114 nM) and TgCPL (EC50 = 71 nM) in vitro. K11777 also inhibited invasion of human fibroblasts by RH tachyzoites by 71% (p = 0.003) and intracellular replication by >99% (p<0.0001). In vivo, a single dose of K11777 led to 100% survival of chicken embryos in an model of acute toxoplasmosis (p = 0.015 Cox regression analysis). Therefore, K11777 shows promise as a novel therapeutic agent in the treatment of toxoplasmosis, and may prove to be a broadly effective anti-parasitic agent.
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Affiliation(s)
- Juan D. Chaparro
- Department of Pediatrics, Division of Infectious Diseases, Rady Children's Hospital, University of California, San Diego, School of Medicine, La Jolla, California, United States of America
| | - Timmy Cheng
- Department of Pathology, University of California, San Diego School of Medicine, La Jolla, California, United States of America
| | - Uyen Phuong Tran
- Department of Pathology, University of California, San Diego School of Medicine, La Jolla, California, United States of America
| | - Rosa M. Andrade
- Department of Medicine, Division of Infectious Diseases, University of California, Irvine School of Medicine, Irvine, California, United States of America
| | - Sara B. T. Brenner
- Department of Pathology, University of California, San Diego School of Medicine, La Jolla, California, United States of America
| | - Grace Hwang
- Department of Pathology, University of California, San Diego School of Medicine, La Jolla, California, United States of America
| | - Shara Cohn
- Department of Pathology, University of California, San Diego School of Medicine, La Jolla, California, United States of America
| | - Ken Hirata
- Department of Pathology, University of California, San Diego School of Medicine, La Jolla, California, United States of America
| | - James H. McKerrow
- Department of Pharmacy, Skaggs School of Pharmacy and Pharmaceutical Science, University of California, San Diego, La Jolla, California, United States of America
| | - Sharon L. Reed
- Department of Pathology, University of California, San Diego School of Medicine, La Jolla, California, United States of America
- * E-mail:
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17
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Romano JD, Nolan SJ, Porter C, Ehrenman K, Hartman EJ, Hsia RC, Coppens I. The parasite Toxoplasma sequesters diverse Rab host vesicles within an intravacuolar network. J Cell Biol 2017; 216:4235-4254. [PMID: 29070609 PMCID: PMC5716271 DOI: 10.1083/jcb.201701108] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 07/28/2017] [Accepted: 09/08/2017] [Indexed: 02/01/2023] Open
Abstract
Many intracellular pathogens subvert host membrane trafficking pathways to promote their replication. Toxoplasma multiplies in a membrane-bound parasitophorous vacuole (PV) that interacts with mammalian host organelles and intercepts Golgi Rab vesicles to acquire sphingolipids. The mechanisms of host vesicle internalization and processing within the PV remain undefined. We demonstrate that Toxoplasma sequesters a broad range of Rab vesicles into the PV. Correlative light and electron microscopy analysis of infected cells illustrates that intravacuolar Rab1A vesicles are surrounded by the PV membrane, suggesting a phagocytic-like process for vesicle engulfment. Rab11A vesicles concentrate to an intravacuolar network (IVN), but this is reduced in Δgra2 and Δgra2Δgra6 parasites, suggesting that tubules stabilized by the TgGRA2 and TgGRA6 proteins secreted by the parasite within the PV contribute to host vesicle sequestration. Overexpression of a phospholipase TgLCAT, which is localized to the IVN, results in a decrease in the number of intravacuolar GFP-Rab11A vesicles, suggesting that TgLCAT controls lipolytic degradation of Rab vesicles for cargo release.
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Affiliation(s)
- Julia D. Romano
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD,Julia D. Romano:
| | - Sabrina J. Nolan
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD
| | - Corey Porter
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD
| | - Karen Ehrenman
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD
| | - Eric J. Hartman
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD
| | - Ru-ching Hsia
- Electron Microscopy Core Imaging Facility, University of Maryland Baltimore, Baltimore, MD
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD,Correspondence to Isabelle Coppens: ;
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18
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Abstract
Globally, nearly 2 billion people are infected with the intracellular protozoan Toxoplasma gondii1. This persistent infection can cause severe disease in immunocompromised people and is epidemiologically linked to major mental illnesses2 and cognitive impairment3. There are currently no options for curing this infection. The lack of effective therapeutics is due partly to a poor understanding of essential pathways that maintain this long-term infection. Although it is known that Toxoplasma replicates slowly within intracellular cysts demarcated with a cyst wall, precisely how it sustains itself and remodels organelles in this niche is unknown. Here we identify a key role for proteolysis within the parasite lysosomal organelle (the vacuolar compartment or VAC) in turnover of autophagosomes and persistence during neural infection. We found that disrupting a VAC-localized cysteine protease compromised VAC digestive function and markedly reduced chronic infection. Death of parasites lacking the VAC protease was preceded by accumulation of undigested autophagosomes in the parasite cytoplasm. These findings suggest an unanticipated function for parasite lysosomal degradation in chronic infection and identify an intrinsic role for autophagy in the T. gondii parasite and its close relatives. This work also identifies a key element of Toxoplasma persistence and suggests that VAC proteolysis is a prospective target for pharmacologic development.
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Cotton JA, Amat CB, Buret AG. Disruptions of Host Immunity and Inflammation by Giardia Duodenalis: Potential Consequences for Co-Infections in the Gastro-Intestinal Tract. Pathogens 2015; 4:764-92. [PMID: 26569316 PMCID: PMC4693164 DOI: 10.3390/pathogens4040764] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/04/2015] [Accepted: 11/05/2015] [Indexed: 12/11/2022] Open
Abstract
Giardia duodenalis (syn. G. intestinalis, or G. lamblia) is a leading cause of waterborne diarrheal disease that infects hundreds of millions of people annually. Research on Giardia has greatly expanded within the last few years, and our understanding of the pathophysiology and immunology on this parasite is ever increasing. At peak infection, Giardia trophozoites induce pathophysiological responses that culminate in the development of diarrheal disease. However, human data has suggested that the intestinal mucosa of Giardia-infected individuals is devoid of signs of overt intestinal inflammation, an observation that is reproduced in animal models. Thus, our understanding of host inflammatory responses to the parasite remain incompletely understood and human studies and experimental data have produced conflicting results. It is now also apparent that certain Giardia infections contain mechanisms capable of modulating their host’s immune responses. As the oral route of Giardia infection is shared with many other gastrointestinal (GI) pathogens, co-infections may often occur, especially in places with poor sanitation and/or improper treatment of drinking water. Moreover, Giardia infections may modulate host immune responses and have been found to protect against the development of diarrheal disease in developing countries. The following review summarizes our current understanding of the immunomodulatory mechanisms of Giardia infections and their consequences for the host, and highlights areas for future research. Potential implications of these immunomodulatory effects during GI co-infection are also discussed.
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Affiliation(s)
- James A Cotton
- Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.
| | - Christina B Amat
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
- Inflammation Research Network, University of Calgary, Calgary, AB T2N 1N4, Canada.
- Host-Parasite Interactions, University of Calgary, Calgary, AB T2N 1N4, Canada.
| | - Andre G Buret
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
- Inflammation Research Network, University of Calgary, Calgary, AB T2N 1N4, Canada.
- Host-Parasite Interactions, University of Calgary, Calgary, AB T2N 1N4, Canada.
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20
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Secretion of Polypeptide Crystals from Tetrahymena thermophila Secretory Organelles (Mucocysts) Depends on Processing by a Cysteine Cathepsin, Cth4p. EUKARYOTIC CELL 2015; 14:817-33. [PMID: 26092918 DOI: 10.1128/ec.00058-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 06/10/2015] [Indexed: 01/26/2023]
Abstract
In many organisms, sophisticated mechanisms facilitate release of peptides in response to extracellular stimuli. In the ciliate Tetrahymena thermophila, efficient peptide secretion depends on specialized vesicles called mucocysts that contain dense crystalline cores that expand rapidly during exocytosis. Core assembly depends of endoproteolytic cleavage of mucocyst proproteins by an aspartyl protease, cathepsin 3 (CTH3). Here, we show that a second enzyme identified by expression profiling, Cth4p, is also required for processing of proGrl proteins and for assembly of functional mucocysts. Cth4p is a cysteine cathepsin that localizes partially to endolysosomal structures and appears to act downstream of, and may be activated by, Cth3p. Disruption of CTH4 results in cells (Δcth4) that show aberrant trimming of Grl proproteins, as well as grossly aberrant mucocyst exocytosis. Surprisingly, Δcth4 cells succeed in assembling crystalline mucocyst cores. However, those cores do not undergo normal directional expansion during exocytosis, and they thus fail to efficiently extrude from the cells. We could phenocopy the Δcth4 defects by mutating conserved catalytic residues, indicating that the in vivo function of Cth4p is enzymatic. Our results indicate that as for canonical proteins packaged in animal secretory granules, the maturation of mucocyst proproteins involves sequential processing steps. The Δcth4 defects uncouple, in an unanticipated way, the assembly of mucocyst cores and their subsequent expansion and thereby reveal a previously unsuspected aspect of polypeptide secretion in ciliates.
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21
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Identification and characterization of a cathepsin-L-like peptidase in Eimeria tenella. Parasitol Res 2014; 113:4335-48. [DOI: 10.1007/s00436-014-4107-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 08/26/2014] [Indexed: 11/26/2022]
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22
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Abstract
The protozoan parasite Toxoplasma gondii resides within a nonfusogenic vacuole during intracellular replication. Although the limiting membrane of this vacuole provides a protective barrier to acidification and degradation by lysosomal hydrolases, it also physically segregates the parasite from the host cytosol. Accordingly, it has been suggested that T. gondii acquires material from the host via membrane channels or transporters. The ability of the parasite to internalize macromolecules via endocytosis during intracellular replication has not been tested. Here, we show that Toxoplasma ingests host cytosolic proteins and digests them using cathepsin L and other proteases within its endolysosomal system. Ingestion was reduced in mutant parasites lacking an intravacuolar network of tubular membranes, implicating this apparatus as a possible conduit for trafficking to the parasite. Genetic ablation of proteins involved in the pathway is associated with diminished parasite replication and virulence attenuation. We show that both virulent type I and avirulent type II strain parasites ingest and digest host-derived protein, indicating that the pathway is not restricted to highly virulent strains. The findings provide the first definitive evidence that T. gondii internalizes proteins from the host during intracellular residence and suggest that protein digestion within the endolysosomal system of the parasite contributes to toxoplasmosis. Toxoplasma gondii causes significant disease in individuals with weak immune systems. Treatment options for this infection have drawbacks, creating a need to understand how this parasite survives within the cells it infects as a prelude to interrupting its survival strategies. This study reveals that T. gondii internalizes proteins from the cytoplasm of the cells it infects and degrades such proteins within a digestive compartment within the parasite. Disruption of proteins involved in the pathway reduced parasite replication and lessened disease severity. The identification of a novel parasite ingestion pathway opens opportunities to interfere with this process and improve the outcome of infection.
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Kumar S, Briguglio JS, Turkewitz AP. An aspartyl cathepsin, CTH3, is essential for proprotein processing during secretory granule maturation in Tetrahymena thermophila. Mol Biol Cell 2014; 25:2444-60. [PMID: 24943840 PMCID: PMC4142616 DOI: 10.1091/mbc.e14-03-0833] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
In animal cells, the assembly of dense cores in secretory granules is controlled by proteolytic processing of proproteins. The same phenomenon occurs in the ciliate Tetrahymena thermophila, but the proteases involved appear to be highly unrelated, suggesting that similar regulatory mechanisms have different molecular origins. In Tetrahymena thermophila, peptides secreted via dense-core granules, called mucocysts, are generated by proprotein processing. We used expression profiling to identify candidate processing enzymes, which localized as cyan fluorescent protein fusions to mucocysts. Of note, the aspartyl cathepsin Cth3p plays a key role in mucocyst-based secretion, since knockdown of this gene blocked proteolytic maturation of the entire set of mucocyst proproteins and dramatically reduced mucocyst accumulation. The activity of Cth3p was eliminated by mutation of two predicted active-site mutations, and overexpression of the wild-type gene, but not the catalytic-site mutant, partially rescued a Mendelian mutant defective in mucocyst proprotein processing. Our results provide the first direct evidence for the role of proprotein processing in this system. Of interest, both localization and the CTH3 disruption phenotype suggest that the enzyme provides non–mucocyst-related functions. Phylogenetic analysis of the T. thermophila cathepsins, combined with prior work on the role of sortilin receptors in mucocyst biogenesis, suggests that repurposing of lysosomal enzymes was an important step in the evolution of secretory granules in ciliates.
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Affiliation(s)
- Santosh Kumar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Joseph S Briguglio
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Aaron P Turkewitz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
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Characterization of the chloroquine resistance transporter homologue in Toxoplasma gondii. EUKARYOTIC CELL 2014; 13:1360-70. [PMID: 24859994 DOI: 10.1128/ec.00027-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Mutations in the Plasmodium falciparum chloroquine resistance transporter (PfCRT) protein confer resistance to the antimalarial drug chloroquine. PfCRT localizes to the parasite digestive vacuole, the site of chloroquine action, where it mediates resistance by transporting chloroquine out of the digestive vacuole. PfCRT belongs to a family of transporter proteins called the chloroquine resistance transporter family. CRT family proteins are found throughout the Apicomplexa, in some protists, and in plants. Despite the importance of PfCRT in drug resistance, little is known about the evolution or native function of CRT proteins. The apicomplexan parasite Toxoplasma gondii contains one CRT family protein. We demonstrate that T. gondii CRT (TgCRT) colocalizes with markers for the vacuolar (VAC) compartment in these parasites. The TgCRT-containing VAC is a highly dynamic organelle, changing its morphology and protein composition between intracellular and extracellular forms of the parasite. Regulated knockdown of TgCRT expression resulted in modest reduction in parasite fitness and swelling of the VAC, indicating that TgCRT contributes to parasite growth and VAC physiology. Together, our findings provide new information on the role of CRT family proteins in apicomplexan parasites.
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Giardia duodenalis cathepsin B proteases degrade intestinal epithelial interleukin-8 and attenuate interleukin-8-induced neutrophil chemotaxis. Infect Immun 2014; 82:2772-87. [PMID: 24733096 DOI: 10.1128/iai.01771-14] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Giardia duodenalis (syn. G. intestinalis, G. lamblia) infections are a leading cause of waterborne diarrheal disease that can also result in the development of postinfectious functional gastrointestinal disorders via mechanisms that remain unclear. Parasite numbers exceed 10(6) trophozoites per centimeter of gut at the height of an infection. Yet the intestinal mucosa of G. duodenalis-infected individuals is devoid of signs of overt inflammation. G. duodenalis infections can also occur concurrently with infections with other proinflammatory gastrointestinal pathogens. Little is known of whether and how this parasite can attenuate host inflammatory responses induced by other proinflammatory stimuli, such as a gastrointestinal pathogen. Identifying hitherto-unrecognized parasitic immunomodulatory pathways, the present studies demonstrated that G. duodenalis trophozoites attenuate secretion of the potent neutrophil chemoattractant interleukin-8 (CXCL8); these effects were observed in human small intestinal mucosal tissues and from intestinal epithelial monolayers, activated through administration of proinflammatory interleukin-1β or Salmonella enterica serovar Typhimurium. This attenuation is caused by the secretion of G. duodenalis cathepsin B cysteine proteases that degrade CXCL8 posttranscriptionally. Furthermore, the degradation of CXCL8 via G. duodenalis cathepsin B cysteine proteases attenuates CXCL8-induced chemotaxis of human neutrophils. Taken together, these data demonstrate for the first time that G. duodenalis trophozoite cathepsins are capable of attenuating a component of their host's proinflammatory response induced by a separate proinflammatory stimulus.
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Cirelli KM, Gorfu G, Hassan MA, Printz M, Crown D, Leppla SH, Grigg ME, Saeij JPJ, Moayeri M. Inflammasome sensor NLRP1 controls rat macrophage susceptibility to Toxoplasma gondii. PLoS Pathog 2014; 10:e1003927. [PMID: 24626226 PMCID: PMC3953412 DOI: 10.1371/journal.ppat.1003927] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 12/21/2013] [Indexed: 12/22/2022] Open
Abstract
Toxoplasma gondii is an intracellular parasite that infects a wide range of warm-blooded species. Rats vary in their susceptibility to this parasite. The Toxo1 locus conferring Toxoplasma resistance in rats was previously mapped to a region of chromosome 10 containing Nlrp1. This gene encodes an inflammasome sensor controlling macrophage sensitivity to anthrax lethal toxin (LT) induced rapid cell death (pyroptosis). We show here that rat strain differences in Toxoplasma infected macrophage sensitivity to pyroptosis, IL-1β/IL-18 processing, and inhibition of parasite proliferation are perfectly correlated with NLRP1 sequence, while inversely correlated with sensitivity to anthrax LT-induced cell death. Using recombinant inbred rats, SNP analyses and whole transcriptome gene expression studies, we narrowed the candidate genes for control of Toxoplasma-mediated rat macrophage pyroptosis to four genes, one of which was Nlrp1. Knockdown of Nlrp1 in pyroptosis-sensitive macrophages resulted in higher parasite replication and protection from cell death. Reciprocally, overexpression of the NLRP1 variant from Toxoplasma-sensitive macrophages in pyroptosis-resistant cells led to sensitization of these resistant macrophages. Our findings reveal Toxoplasma as a novel activator of the NLRP1 inflammasome in rat macrophages. Inflammasomes are multiprotein complexes that are a major component of the innate immune system. They contain “sensor” proteins that are responsible for detecting various microbial and environmental danger signals and function by activating caspase-1, an enzyme that mediates cleavage and release of the pro-inflammatory cytokines, IL-1β and IL-18. Toxoplasma gondii is a highly successful protozoan parasite capable of infecting a wide range of host species that have variable levels of resistance. Rat strains have been previously shown to vary in their susceptibility to this parasite. We report here that rat macrophages from different inbred strains also vary in sensitivity to Toxoplasma induced lysis. We find that NLRP1, an inflammasome sensor whose only known agonist is anthrax LT, is also activated by Toxoplasma infection. In rats there is a perfect correlation between NLRP1 sequence and macrophage sensitivity to Toxoplasma-induced rapid cell death, inhibition of parasite proliferation, and IL-1β/IL-18 processing. Nlrp1 genes from sensitive rat macrophages can confer sensitivity to this rapid cell death when expressed in Toxoplasma resistant rat macrophages. Our findings suggest Toxoplasma is a new activator of the NLRP1 inflammasome.
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Affiliation(s)
- Kimberly M. Cirelli
- Massachusetts Institute of Technology, Department of Biology, Cambridge, Massachusetts, United States of America
| | - Gezahegn Gorfu
- Molecular Parasitology Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
| | - Musa A. Hassan
- Massachusetts Institute of Technology, Department of Biology, Cambridge, Massachusetts, United States of America
| | - Morton Printz
- Department of Pharmacology, University of California-San Diego, La Jolla, California, United States of America
| | - Devorah Crown
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
| | - Stephen H. Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
| | - Michael E. Grigg
- Molecular Parasitology Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
- * E-mail: (MEG); (JPJS); (MM)
| | - Jeroen P. J. Saeij
- Massachusetts Institute of Technology, Department of Biology, Cambridge, Massachusetts, United States of America
- * E-mail: (MEG); (JPJS); (MM)
| | - Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
- * E-mail: (MEG); (JPJS); (MM)
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Abstract
Induction of immunity that limits Toxoplasma gondii infection in mice is critically dependent on the activation of the innate immune response. In this study, we investigated the role of cytoplasmic nucleotide-binding domain and leucine-rich repeat containing a pyrin domain (NLRP) inflammasome sensors during acute toxoplasmosis in mice. We show that in vitro Toxoplasma infection of murine bone marrow-derived macrophages activates the NLRP3 inflammasome, resulting in the rapid production and cleavage of interleukin-1β (IL-1β), with no measurable cleavage of IL-18 and no pyroptosis. Paradoxically, Toxoplasma-infected mice produced large quantities of IL-18 but had no measurable IL-1β in their serum. Infection of mice deficient in NLRP3, caspase-1/11, IL-1R, or the inflammasome adaptor protein ASC led to decreased levels of circulating IL-18, increased parasite replication, and death. Interestingly, mice deficient in NLRP1 also displayed increased parasite loads and acute mortality. Using mice deficient in IL-18 and IL-18R, we show that this cytokine plays an important role in limiting parasite replication to promote murine survival. Our findings reveal T. gondii as a novel activator of the NLRP1 and NLRP3 inflammasomes in vivo and establish a role for these sensors in host resistance to toxoplasmosis. Inflammasomes are multiprotein complexes that are a major component of the innate immune system. They contain “sensor” proteins that are responsible for detecting various microbial and environmental danger signals and function by activating caspase-1, an enzyme that mediates cleavage and release of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18. Toxoplasma gondii is a highly successful protozoan parasite capable of infecting a wide range of host species that have variable levels of resistance. We report here that T. gondii is a novel activator of the NLRP1 and NLRP3 inflammasomes in vivo and establish a role for these sensors in host resistance to toxoplasmosis. Using mice deficient in IL-18 and IL-18R, we show that the IL-18 cytokine plays a pivotal role by limiting parasite replication to promote murine survival.
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Tomavo S, Slomianny C, Meissner M, Carruthers VB. Protein trafficking through the endosomal system prepares intracellular parasites for a home invasion. PLoS Pathog 2013; 9:e1003629. [PMID: 24204248 PMCID: PMC3812028 DOI: 10.1371/journal.ppat.1003629] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Toxoplasma (toxoplasmosis) and Plasmodium (malaria) use unique secretory organelles for migration, cell invasion, manipulation of host cell functions, and cell egress. In particular, the apical secretory micronemes and rhoptries of apicomplexan parasites are essential for successful host infection. New findings reveal that the contents of these organelles, which are transported through the endoplasmic reticulum (ER) and Golgi, also require the parasite endosome-like system to access their respective organelles. In this review, we discuss recent findings that demonstrate that these parasites reduced their endosomal system and modified classical regulators of this pathway for the biogenesis of apical organelles.
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Affiliation(s)
- Stanislas Tomavo
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
- * E-mail:
| | - Christian Slomianny
- Laboratory of Cell Physiology, INSERM U 1003, Université Lille Nord de France, Villeneuve d'Ascq, Lille, France
| | - Markus Meissner
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Vern B. Carruthers
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
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